Effect of morphological deformation on barriers to charge injection at the interface of copper and polyethylene

Barriers to charge injection at polymer/metal interface is key to understanding high field conduction in cables and capacitors. The present paper investigates barriers to charge injection at the interface of copper and polyethylene (PE), one of the most dominant material combination in the power industry, with a focus on morphological deformation. Using computational quantum mechanics in the framework of density functional theory (DFT) barriers to charge injection where calculated showing similar results to previous DFT studies on the interface of Pt, Au, and Ag in terms of the absolute barriers to hole and electron injection. However, states appearing between the Fermi level of Cu and the conduction band of PE where identified leading to the lowering of the barrier to electron injection by about 0.9 eV. These states were due to the morphological deformation that takes place for both the metal and the polymer at the interface. No similar states were identified in the case of Pt, Au and Ag in similar studies. The paper stresses on the importance of considering morphological deformation in lowering the barriers to charge injection in soft metal which is less considered as compared to chemical impurities.